Artificial turf system comprising hydrophobic sand

ABSTRACT

The present application relates to an artificial turf system, comprising an elastic substrate layer, an artificial turf carpet applied on the elastic substrate layer, and a first filler material which is filled into the artificial turf carpet, wherein the first filler material comprises a hydrophobic sand, and the use thereof as sports artificial turf.

The present application relates to an artificial turf system, comprising hydrophobic sand, and the use thereof as artificial sports turf.

Artificial turf has already been used for several decades as an alternative to natural grass, both in sports and in landscaping. Depending on the use, in sports and landscaping the artificial turf has to fulfil different requirements. For example, the structure, the finish and the appearance of the artificial turf surface varies depending on the technical requirements placed on the artificial grass in question. This is achieved, for example, by the use of different yarns, the number of filaments used, the filament length, etc.

However, high-performance artificial turf consists not only of the visible artificial turf surface. Various layers, which ensure, inter alia, improved damping and drainage of the artificial turf surface, are located under the artificial turf surface. In particular in sports, artificial turf systems are used which comprise an elastic carrier layer or substrate layer under the artificial turf surface. The elastic carrier layer under the artificial turf surface ensures that the force build-up on the artificial turf is ensured. Furthermore, the artificial turf systems in sports are filled with different infill materials, such as sand, cork or mixtures thereof. Such infill materials provide the artificial turf system with a firm hold, and increase the playing properties of the artificial turf system and the resilience. Combined with the elastic carrier layer, the infill materials ensure a damping and significantly contribute to further properties of the artificial turf system such as the ball bouncing behavior, the ball rolling behavior, and a minimization of the risk of injury.

A further demand on artificial turf systems in sports is that good play thereon should be possible even after rain and in cold temperatures. This requires, inter alia, that the surface of the artificial turf systems does not freeze at temperatures around the freezing point and does not become too slippery. This means that the rotational resistance of the artificial turf system pursuant to EN 15301-1 as far as possible does not drop too much, even in winter conditions, and preferably remains above 30 Nm.

In the case of the artificial turf systems known from the prior art, comprising infill materials, for sports, in particular when the temperature falls below the freezing point following rain, it is observed that the rainwater bound in the infill material, such as sand, subsequently freezes to form a hard, compact surface, as a result of which the rotational resistance of the artificial turf system is reduced. This problem is particularly clear in the case of the artificial turf systems typically used for sports, comprising exclusively sand as the infill material. It has been found that, after a heavy rain shower (approximately 40 I/m²) and after the rainwater has run off, the residual moisture of quartz sand used as infill material is still over 20 wt. % even. This leads to a significant reduction of the rotational resistance of the artificial turf system (below 30 Nm), and thus to an impairment of the playing properties, in the case of cold weather conditions and a not yet completely dried artificial turf system.

The object of the present invention is therefore that of providing an artificial turf system, in particular for sports, by means of which the above-described disadvantages can be overcome.

This object is achieved according to the invention by an artificial turf system defined in the claims.

Accordingly, the present invention relates to an artificial turf system, comprising an elastic substrate layer, an artificial turf carpet applied on the elastic substrate layer, and a first filler material which is filled into the artificial turf carpet, wherein the first filler material comprises a hydrophobic sand.

For the first time, the artificial turf system according to the invention provides a sand-filled artificial turf system in which the residual moisture of the sand, with which the artificial turf system is filled, is less than 20 wt. %, based on the total weight of the sand that is filled in, after rain and runoff of the rainwater, even in the case of heavy rain showers of over 40 I/m². As a result, the artificial turf system according to the invention does not freeze to a hard, compact surface in winterly weather conditions, even after heavy rain showers. Accordingly, the rotational resistance of the artificial turf system according to the invention remains sufficiently high, even in the case of damp winterly conditions below the freezing point, and is preferably always above 30 Nm. Even after heavy rain showers, the artificial turf system according to the invention exhibits excellent playing properties, in particular also in winter, such as an excellent ball bounce behavior, an excellent ball rolling behavior, a low skid behavior (low risk of slipping), an excellent traction and rotation behavior, and an excellent elasticity. As a result, the risk of injury to players when using the artificial turf system according to the invention, in particular in damp and/or winterly weather conditions, is minimized.

The artificial turf system according to the invention comprises an elastic substrate layer. Within the context of the present invention, any conventional elastic substrate layer, hitherto already used in artificial turf systems or suitable therefor, can be used. These may for example be prefabricated shock pads (shock-absorbing rubber pads or rubber mats) or elastic layers or elastic carrier layers.

Furthermore, the artificial turf system according to the invention comprises an artificial turf carpet applied on the elastic substrate layer. Within the context of the present invention, any conventional artificial turf carpet, hitherto used in artificial turf systems or suitable therefor, can be used.

Furthermore, the artificial turf system according to the invention comprises a first filler material which is filled into the artificial turf carpet and which comprises a hydrophobic sand. The term “hydrophobic sand” denotes sand which exhibits hydrophobic properties and, associated therewith, has low water binding properties. According to the present invention, this may be a sand which inherently has hydrophobic properties, or a sand which has been hydrophobized by modification, for example by surface functionalization.

The hydrophobic sand which the artificial turf system according to the invention comprises is preferably characterized in that it has reduced water binding properties, and thus binds less water/residual water, compared with conventional sand, such as quartz sand, fluvial sand, sea sand, drifting sand, desert sand, and mixtures thereof. Compared with conventional quartz sand, the hydrophobic sand of the artificial turf system according to the invention is for example less able to bind water molecules by forming hydrogen bridge bonds and to agglomerate to a solid layer.

In a preferred embodiment of the artificial turf system according to the invention, the elastic substrate layer comprises a bonded elastic layer, an elastic carrier layer, or shock pads (shock-absorbing rubber pads or rubber mats).

In a preferred embodiment of the artificial turf system according to the invention, the artificial turf carpet applied on the elastic substrate layer is selected from the group consisting of an artificial turf carpet comprising at least one textured yarn, an artificial turf carpet comprising at least one flat yarn, and an artificial turf carpet comprising at least one flat yarn and at least one textured yarn.

In a preferred embodiment of the artificial turf system according to the invention, the hydrophobic sand has a substantially round-grained shape. As a result, the risk of injury to players when using the artificial turf system is reduced. Furthermore, a round-grained sand is less able to agglomerate. Not least, the round-grained sand shape contributes to a reduced wear of the artificial turf fibers compared with a sharp-edged sand shape.

It is furthermore preferred that at least 95 wt. % of the hydrophobic sand has a grain size distribution of 0.2 to 2.0 mm, preferably 0.25 to 1.40 mm, based on the total weight of the hydrophobic sand that is filled in.

Ideally, the hydrophobic sand has a content of fine material, of smaller than 0.063 mm, which is less than or equal to 2 wt. %, based on the total weight of the hydrophobic sand that is filled in.

Furthermore, it is preferred for the content of CaCO₃ in the hydrophobic sand to be less than or equal to 3 wt. % and/or the content of SiO₂ in the hydrophobic sand to be greater than or equal to 96 wt. %, based on the total weight of the hydrophobic sand.

In a further preferred embodiment of the artificial turf system according to the invention, the filling quantity of the hydrophobic sand is 5-20 kg/m².

Ideally, the hydrophobic sand is filled in such that the sand layer in principle has good permeability. This means that the sand layer can be easily permeated by the rainwater of a rain shower falling on the artificial turf system, in order to prevent a build-up of water on the surface of the artificial turf system. Water building up on the artificial turf layer would significantly impair the properties of the artificial turf system, such as the ball bounce behavior, the ball rolling behavior, the skid behavior, and the traction and rotation behavior.

In a further preferred embodiment of the artificial turf system according to the invention, the hydrophobic sand is hydrophobized sand.

The term “hydrophobized sand” includes sand or sand particles which is/are provided with hydrophobic properties by means of surface functionalization. The surface functionalization of the sand/sand particles is preferably formed by hydrophobic molecules which are applied to the sand/sand particles in particular via chemical bonding. Advantageously, the weight fraction of the surface functionalization of the sand/sand particles is less than 5 wt. %, preferably 0.05-3 wt. %, more preferably 0.1-1 wt. %, based on the total weight of the hydrophobized sand/the hydrophobized sand particles.

The sand/sand particles is/are preferably selected from the group consisting of quartz sand, fluvial sand, sea sand, drifting sand, desert sand, and mixtures thereof.

The hydrophobized sand is preferably selected from hydrophobized quartz sand, hydrophobized fluvial sand, hydrophobized sea sand, hydrophobized drifting sand, hydrophobized desert sand, and mixtures thereof. The hydrophobized sand is particularly preferably hydrophobized quartz sand.

According to the present invention, the hydrophobized sand is produced according to conventional surface functionalization methods known to a person skilled in the art. However, for the purpose of environmental protection, the present invention provides that the surface functionalization preferably does not comprise any plastics coating (polymer coating) of the carrier particles, since such particles could be discharged into the environment as microplastic. The surface functionalization methods are preferably hydrophilization methods. A particularly preferred hydrophilization method is silanization.

In a further preferred embodiment of the artificial turf system according to the invention, the hydrophobized sand is silanized sand.

The term “silanized sand” denotes sand or sand particles, respectively, which is/are silanized by means of a silanization method. Within the context of the present invention, in principle any conventional silanization method can be used for producing the silanized sand. For example, the sand to be silanized, preferably quartz sand, fluvial sand, sea sand, drifting sand, desert sand, and mixtures thereof, can be mixed/converted with a suitable silane at ambient temperature, while stirring or during transport in a conveying device, such as a screw conveyor. Subsequently, the sand/silane mixture can either be used directly for use in artificial turf, or can initially undergo a drying process for a few hours at increased temperature. Advantageously, the silane used for the silanization is used in the form of an aqueous formulation, which, in addition to the silane, optionally contains a surfactant, for example an ethoxylated secondary fatty alcohol. Preferably, the fraction of the silane in the aqueous formulation is 1-25 wt. %, more preferably 1-10 wt. %, based on the total weight of the aqueous formulation.

Preferably, the silane used for the silanization is selected from the group consisting of alkoxysilanes, in particular alkyl alkoxysilanes and alkyl siloxanes. Particularly preferably, the silane used is selected from the group consisting of an alkyl trimethoxysilane, an alkyl triethoxysilane, an alkyl oligosiloxane, an alkyl polysiloxane, and/or mixtures thereof, wherein the alkyl group preferably comprises an alkyl group having 3-12 carbon atoms, preferably 6-10 carbon atoms, and most preferably 8 carbon atoms, or mixtures thereof. (Please check for accuracy). The silane used is particularly preferably an alkyl triethoxysilane, in particular triethoxyoctylsilane. Most preferably, the silane is the silane formulations MasterPel 708, 793 or 903 by the company BASF.

The silanized sand is particularly preferably sand, preferably quartz sand, fluvial sand, sea sand, drifting sand, desert sand, and mixtures thereof, which is silanized with an alkyl trimethoxysilane, an alkyl triethoxysilane, an alkyl siloxane, an alkyl oligosiloxane, an alkyl polysiloxane, and/or mixtures thereof. In particular, the silanized sand is a sand which is silanized with an alkyl triethoxysilane, in particular triethoxyoctylsilane, or the silane formulation MasterPel 708, 793 or 903 by the company BASF.

Advantageously, the weight fraction of the silanization is 5 wt. %, preferably 0.001-3 wt. %, more preferably 0.001-1 wt. %, based on the total weight of the silanized sand. Thus, the amount is sufficient both to completely hydrophobize the particle surface, and to work in a resource-saving manner.

In a preferred embodiment of the artificial turf system according to the invention, the system further comprises a second filler material which is filled into the artificial turf carpet.

The second filler material is preferably selected from the group consisting of cork, olive stone waste, nut shells, wood, rubber granulate and/or mixtures thereof. More preferably, the second filler material is selected from the group consisting of cork, olive stone waste, nut shells, wood and/or mixtures thereof.

The present invention furthermore relates to the use of the artificial turf system according to the invention as sports artificial turf.

On account of its structure and the resulting properties, such as an excellent ball bouncing behavior, an excellent ball rolling behavior, a low skid behavior (low risk of slipping), an excellent traction and rotation behavior, and an excellent elasticity, the turf system according to the invention is suitable in particular as sports artificial turf in football, hockey, rugby, American football, tennis and golf, wherein in principle any other type of sport can also be played on the sports artificial turf system.

The present invention is illustrated in greater detail in the following, with reference to the following examples.

Example 1

Production of Hydrophobized Sand

1 kg of a round-grained quartz sand having a grain size distribution of 0.71-1.25 mm was provided, and this was mixed with 30 ml BASF Masterpel 793, at room temperature, while stirring. The sand was subsequently dried for 24 h at 60° C. An easily pourable product was obtained.

Example 2

Testing the Properties of the Hydrophobized Sand

The residual water content and the water drainage behavior of the hydrophobized quartz sand produced in example 1 and of a non-hydrophobized quartz sand having the same grain size distribution (comparison) were examined using the following test apparatus.

A Büchner funnel having a diameter of 10 cm and equipped with a sieve insert was filled with a volume of 265 ml of the respective sand. Subsequently, 300 ml tap water was applied to the sand using a sprinkler, and the water draining off was collected in a measuring cylinder.

The amount of water that had drained off after 20 minutes was determined. In addition, the residual moisture of the respective sand sample was subsequently determined. The results are shown in table 1.

TABLE 1 Water amount drained Residual moisture Sand off after 20 min (ml) (wt. %) Hydrophobized sand from 220 16 example 1 Non-hydrophobized sand as 180 23 a comparison

In the case of both sands, the water drained off rapidly and was completely drained off after at most 20 minutes. The hydrophilization made it possible for the residual moisture of the sand from example 1 to be reduced by approximately 30% compared with the non-hydrophobized sand.

Example 3

Testing of the rotational resistance of an artificial turf system according to the invention after wetting and in cold conditions

Two rectangular stainless steel troughs having a flat base comprising drainage holes, base area 0.5 m², were each equipped with a 30 mm elastic layer. In each case an artificial turf carpet, consisting of a slit film polyethylene yarn, tufted together (12,000 dtex, thickness 0.130 mm) and a textured polyethylene yarn (8,000 dtex, thickness 0.320 mm), gauge 3/8″″, having a pole height of 20 and 17 mm, respectively, was placed thereon. Subsequently, the artificial turf carpet was in each case filled with sand to a height of approximately 17 mm, wherein the hydrophobized quartz sand from example 1 was used in the first stainless steel trough, and the non-hydrophobized quartz sand was used in the second stainless steel trough, as a comparison.

In order to simulate heavy rain, in each case 20 I water was poured uniformly over the surface in question, and there was a wait of 20 minutes in each case. In this time, the water drained off completely in each case. Subsequently, the two stainless steel troughs were cooled for 3 days at −5° C. ambient temperature, and subsequently the rotational resistance was determined. The results are shown in table 2.

TABLE 2 Rotational resistance Sand after freezing (Nm) Hydrophobized sand from example 1 37 Non-hydrophobized sand as a comparison 22

It has been found that the rotational resistance of the artificial turf system according to the invention, which is filled in with hydrophobic sand, has a significantly higher rotational resistance (1.7 times greater) after wet conditions and frost than an artificial turf system which is not filled in with hydrophobic sand. 

1. An artificial turf system, comprising: an elastic substrate layer, an artificial turf carpet applied on the elastic substrate layer, and a first filler material which is filled into the artificial turf carpet, wherein the first filler material comprises a hydrophobic sand.
 2. The artificial turf system according to claim 1, wherein the elastic substrate layer comprises a bonded elastic layer, an elastic carrier layer, or shock pads.
 3. The artificial turf system according to claim 1, wherein the artificial turf carpet is selected from an artificial turf carpet comprising at least one textured yarn, an artificial turf carpet comprising at least one flat yarn, or an artificial turf carpet comprising at least one flat yarn and at least one textured yarn.
 4. The artificial turf system according to claim 1, wherein the hydrophobic sand has a substantially round-grained shape.
 5. The artificial turf system according to claim 1, wherein at least 95% of the hydrophobic sand has a grain size distribution of 0.2 to 2.0 mm.
 6. The artificial turf system according to claim 1, wherein the hydrophobic sand has an SiO2 fraction of ≥96% and/or a CaCO₃ fraction of ≥3%.
 7. The artificial turf system according t to claim 1, wherein the filling quantity of the hydrophobic sand is 5-20 kg/m².
 8. The artificial turf system according to claim 1, wherein the hydrophobic sand is hydrophobized sand.
 9. The artificial turf system according to claim 8, wherein the hydrophobized sand is selected from hydrophobized quartz sand, hydrophobized fluvial sand, hydrophobized sea sand, hydrophobized drifting sand, hydrophobized desert sand, and mixtures thereof.
 10. The artificial turf system according to claim 8, wherein the hydrophobized sand is silanized sand.
 11. The artificial turf system according to claim 10, wherein the silanized sand is selected from sand which is silanized with alkyl trimethoxysilane, alkyl triethoxysilane, alkyl oligosiloxane, alkyl polysiloxane, or mixtures thereof.
 12. The artificial turf system according to claim 10, wherein the weight fraction of the silanization comprises ≤5 wt. %, preferably 0.001-3 wt. %, more preferably 0.001-1 wt. %, based on the total weight of the silanized sand.
 13. The artificial turf system according to claim 1, further comprising a second filler material which is filled into the artificial turf carpet.
 14. The artificial turf system according to claim 13, wherein the second filler material is selected from cork, olive stone waste, nut shells, wood, rubber granules or mixtures thereof.
 15. The artificial turf system according to claim 1, wherein the artificial turn system is used as sports artificial turf.
 16. An artificial turf system having an elastic substrate and an artificial turf carpet on top of the elastic substrate, the artificial turf carpet filled with a layer of hydrophobized sand having a residual moisture of less than 20% by weight (20 wt. %) after water falls uniformly over a surface of the artificial turf system and is drained off after a period of time.
 17. The artificial turf system of claim 16, wherein the layer of hydrophobized sand has a height of approximately 17 mm.
 18. The artificial turf system of claim 16, wherein the period of time is 20 minutes.
 19. The artificial turf system of claim 16, wherein the hydrophobized sand provides the artificial turf system with a rotational resistance of 30 Nm or more.
 20. The artificial turf system of claim 16, wherein the hydrophobized sand provides the artificial turf system with a rotational resistance of 30 Nm or more at −5° C. ambient temperature. 